These experiments are designed to better understand the nature and consequences of interactions between intestinal epithelial cells and polymorphonuclear leukocytes (neutrophils). Such interactions histologically define "active" inflammation as it occurs in Inflammatory Bowel Disease (IBD) and certain gastrointestinal infections. Indeed, the epithelial cells can promote such interactions with neutrophils when they detect surface pathogens such as Salmonella typhimurium, and recognition of such also permits us to include experimentation of epithelial responses to Salmonella. To model such interactions we use human epithelial intestinal cell lines, which have been predictive of events in this area in natural human intestine (and we use the latter to confirm our primary observations derived from models). First we will pursue findings, which indicate that adenosine mediated signaling via a 5'-AMP-CD73-A2bReceptor axis is the basis for directly mediated intestinal fluid secretion in response to neutrophils. Our first specific aim is this to define the neutrophil compartment from which 5 '-AMP originates; define biochemical compartmentalization of CD73 and A2bR on epithelia's analyze asymmetric A2bR desensitization; and assess polarized transcriptional regulation by adenosine as well as adenosine feed-back effects on neutrophils. In the second specific aim we will use transposing mutagenesis to explore further Salmonella genes necessary for productive interactions with epithelia and, conversely, examine epithelial small GTPases to define contributions of these epithelial peptides to such interactions. The third specific aim will analyze transepithelial signaling important in induction of the epithelial pro-inflammatory response to S. typhimurium. Lastly, we will analyze natural signaling methods of down regulation this epithelial pro-inflammatory pathway, including a novel suggestion of effects with dual impact not only on inflammation, but also on a key component of an epithelial proliferation pathway. Restricted use of an animal model of IBD will verify the in vivo efficacy of activation of natural anti-inflammatory pathways. In aggregate, such data should provide insights into mechanisms of neutrophil-intestinal epithelial crosstalk during active inflammation and may thus provide new clues for strategic interference in these often-deleterious intercellular interactions.